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Thread: A2091 14Mhz SCSI mod

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    Lightbulb A2091 14MHz SCSI mod

    Hello my fellow AmiBayer's! As you probably know by now, I have developed a nasty habit of hacking my Amiga's with the intention of speeding them up in various ways.

    So here is my implementation of the Official C= A2091 speedup mod. The reason I say "Official" is because it's mostly taken from the A2091 service manual. The really nice thing about this hack is that it's a very simple thing to do and a perfect DIY project!

    First you need to make sure you have the WD33C93"A" (or the AMD "A" version) SCSI chip on the A2091.

    Then following the service manual instructions you cut the trace for the upper 2 pins of JP201. Then you IGNORE the service manual instructions to jumper the lower 2 pins of JP201 and FOLLOW my instructions to jumper the outer 2 pins (Pins 1 & 3) and your SCSI chip should now happily be running from a 14 MHz clock!

    I've tested this with C= V6.6 and V7.0 ROM's as well as Ralph Babel's Guru ROM. I recommend the C= 7.0 ROM's or Guru ROM for best performance. Using RSCP I've benchmarked transfers around 3.1 MB/sec on my A2000. Enjoy!

    Note: See post #36 for info about the NEW 33C93A_Config tool. The actual transfer rates will vary depending on the speed of the hard drive, ROM's, CPU speed, Buster ZorroII vs. SuperBuster ZorroII and your choice of benchmark program!
    Attached Thumbnails Attached Thumbnails A2091A.JPG   A2091B.PNG   A2091c.jpg  
    Attached Files Attached Files
    Last edited by SpeedGeek; 23rd June 2014 at 16:34.

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    Awesome stuff! It really is all about squeezing every last drop of performance out of every part of the system, isn't it?

    Thinking about accelerating your A1200? Check out my buyer's guide.

    Projects past and present: Amiga 2000/030 | Amiga 3000/040 | Amiga 4000/060

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    BANNED Kin Hell's Avatar
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    Yes Andy, you're dead right & 3Mb/Sec on an A2K is not to be sniffed at.
    Most impressive to say the least.

    Kin

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    Could this be done to the SCSI controller on the A590 as well? Just curious, as the A2000 and A500 are somewhat related....
    The future's so Retr0bright, I gotta wear shades.....

    As rkauer said:-
    "Retro computers seems like an orgasm: it is always better to have a real one than fake it".

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    Amiga tweaker Amibayer! Buzzfuzz's Avatar
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    Works

    Getting 1,5 MB/ sec with a standard A2000 with Sysinfo.
    Shall give it some memory now, see if that speeds it up more.

    Edit: Yep, FULLY confirmed, with 8MB of fast ram, 2.4MB/Sec even with 6.6 roms and an 68000
    My A2091 has 0MB memory, so that's why it was a bit tad slower on the first test.
    Wonderful Indonesia

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    Do you think this hack is appliable to the A2090A?


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    Quote Originally Posted by Buzzfuzz View Post
    Works

    Getting 1,5 MB/ sec with a standard A2000 with Sysinfo.
    Shall give it some memory now, see if that speeds it up more.

    Edit: Yep, FULLY confirmed, with 8MB of fast ram, 2.4MB/Sec even with 6.6 roms and an 68000
    My A2091 has 0MB memory, so that's why it was a bit tad slower on the first test.
    Brilliant!

    Kin

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    @Merlin
    Yes, it could be done on the A590 but not quite as easily as the A2091. You would have to cut the trace to clock pin of the SCSI chip and run a couple more jumpers to the 74LS86 to create the 14 Mhz clock. If there is enough interest in doing this and I can find the time I'll make a schematic for this. Of course, some clever A590 owner could easily beat me to it!

    @8bitbubsy
    That's a very good question! Hopefully, some clever A2090A owner can beat me to answering this question as well!

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    Quote Originally Posted by Kin Hell View Post
    Brilliant!
    Kin
    Yep, easy, simple mod, make sure you have the fastram and that it's good and stable.
    Wonderful Indonesia

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    Quote Originally Posted by Buzzfuzz View Post
    Edit: Yep, FULLY confirmed, with 8MB of fast ram, 2.4MB/Sec even with 6.6 roms and an 68000
    Wow, that's awesome! That's about the same speed I get from my A3000s native SCSI, to achieve that on an A2000 is very tasty indeed.
    Thinking about accelerating your A1200? Check out my buyer's guide.

    Projects past and present: Amiga 2000/030 | Amiga 3000/040 | Amiga 4000/060

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